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Alexandr A. Nikitin Alexandr S. Serdyukov Anton A. Duchkov 《Computational Geosciences》2018,22(3):775-787
Numerical solution of the eikonal equation is frequently used to compute first-arrival travel times for a given velocity model in seismic applications. Computations for large three-dimensional models become expensive requiring the use of efficient parallel solvers. We present new parallel implementations of the fast sweeping and locking sweeping methods optimized for shared memory systems such as multicore CPUs; we call them block fast sweeping method (BFSM) and block locking sweeping method (BLSM). Proposed methods are based on the domain decomposition approach with a special attention paid to high efficiency of the cache utilization and task execution synchronization. Performance tests on realistic models show high parallel efficiency of 85–95% on modern multicore CPUs and require the same number of iterations to converge as do the serial sweeping methods. We also highlight the importance of properly selecting the stopping criterion in the iterative sweeping methods aiming for a balance between computational time and accuracy of the result required by an application. In particular, we show that in seismic applications one can reach reasonable accuracy of computed travel times while dramatically reducing the number of iterations compared to the case of using the full convergence stopping criterion. 相似文献
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Alexandr V. Vikulin Tatiana Yu. Tveritinova Alexandr G. Ivanchin 《Acta Geophysica》2013,61(2):245-263
The work presents a review of natural-science representations on the rotary motion of matter and its piecewise structure. Development of dense GPS-networks allowed to experimentally confirm the concept of block structures of the geophysical environment and to prove rotary character of block movement. An analysis of both the migration of earthquake sources and the movement of sections of tectonic plates’ borders has allowed to reveal general properties of such movements and to prove their wave nature. It is shown that within the limits of rotational model, blocks and plates are interconnected among themselves by the elastic long-range fields forming a uniform planetary geodynamic field. It is offered to use the geodynamic solutions of rotational model in the one class of phenomena as a basis at the construction of a new geological paradigm — wave moment geodynamics. 相似文献
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Galactic cosmic rays-clouds effect and bifurcation model of the Earth global climate. Part 1. Theory
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Alexey V. Eliseev Alexandr V. Chernokulsky Andrey A. Karpenko Igor I. Mokhov 《Theoretical and Applied Climatology》2010,101(1-2):67-81
An approach to mitigate global warming via sulphur loading in the stratosphere (geoengineering) is studied, employing a large ensemble of numerical experiments with the climate model of intermediate complexity IAP RAS CM. The model is forced by the historical+SRES A1B anthropogenic greenhouse gases+tropospheric sulphates scenario for 1860–2100 with additional sulphur emissions in the stratosphere in the twenty-first century. Different ensemble members are constructed by varying values of the parameters governing mass, horizontal distribution and radiative forcing of the stratospheric sulphates. It is obtained that, given a global loading of the sulphates in the stratosphere, among those studied in this paper latitudinal distributions of geoengineering aerosols, the most efficient one at the global basis is that peaked between 50°N and 70°N and with a somewhat smaller burden in the tropics. Uniform latitudinal distribution of stratospheric sulphates is a little less efficient. Sulphur emissions in the stratosphere required to stop the global temperature at the level corresponding to the mean value for 2000–2010 amount to more than 10 TgS/year in the year 2100. These emissions may be reduced if some warming is allowed to occur in the twenty-first century. For instance, if the global temperature trend S g in every decade of this century is limited not to exceed 0.10 K/decade (0.15 K/decade), geoengineering emissions of 4–14 TgS/year (2–7 TgS/year) would be sufficient. Even if the global warming is stopped, temperature changes in different regions still occur with a magnitude up to 1 K. Their horizontal pattern depends on implied latitudinal distribution of stratospheric sulphates. In addition, for the stabilised global mean surface air temperature, global precipitation decreases by about 10%. If geoengineering emissions are stopped after several decades of implementation, their climatic effect is removed within a few decades. In this period, surface air temperature may grow with a rate of several Kelvins per decade. The results obtained with the IAP RAS CM are further interpreted employing a globally averaged energy–balance climate model. With the latter model, an analytical estimate for sulphate aerosol emissions in the stratosphere required climate mitigation is obtained. It is shown that effective vertical localisation of the imposed radiative forcing is important for geoengineering efficiency. 相似文献
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Strong Tidal Mixing and Ventilation of Cold Intermediate Water at Kashevarov Bank, Sea of Okhotsk 总被引：1，自引：0，他引：1
Konstantin A. Rogachev Eddy C. Carmack Alexandr S. Salomatin 《Journal of Oceanography》2000,56(4):439-447
Tidal mixing at the Kashevarov Bank, Sea of Okhotsk, has been investigated using observations of bottom pressure and currents. The tides are dominated by the diurnal constituents. The water motion over the Bank is predominantly controlled by strong diurnal tidal currents, which bring cold water on the bank from its source, a cold intermediate layer. The temperature fluctuations are about 1.2°C at the southern edge of the bank. The maximum observed velocity is about 164 cm/s at the top of the bank. A superposition of the original diurnal constituents K1 and O1 reveals a strong fortnightly (Mf) variability of the current speed. Tidal-induced mixing is responsible for ventilation of the cold intermediate layer of the Sea of Okhotsk. Strong tidal mixing creates a well-defined tidally mixed front around the bank. This front acts like a barrier separating well-mixed water on the bank from stratified water on its flanks. There is a residual current of the order of 10 cm/s. 相似文献
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Community Structure in the Amber Forest: Study of the Arthropod Syninclusia in the Rovno Amber(Late Eocene of Ukraine) 总被引：1，自引：1，他引：0
Evgeny E.?PERKOVSKY Alexandr P.?RASNITSYN Аnatoly P. VLASKIN Sergej P.?RASNITSYN 《《地质学报》英文版》2010,84(4):954-958
<正>Arthropodan syninclusions in the Late Eocene Rovno amber were examined using x~2 to reveal correlation of the component groups(some taxa of Diptera,ants,aphids,and mites) supposedly indicative of the biocoenotic relationships in the ancient amber forest.Three tightly correlated groups were identified,representing a putative aerial plankton guild(Chironomidae+Ceratopogonidae) and two tree-trunk guilds,one of which (Dolichopodidae+Germaraphis) is possibly connected to more open or/and more hygrophilous habitats than the other(Sciara zone Diptera +"Acarus"rhombeus).The ants were not linked with any of the above components. 相似文献
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Two New Fossil Sawflies (Hymenoptera, Xyelidae, Xyelinae) from the Middle Jurassic of China 总被引：1，自引：1，他引：0
Two new genera with two new species of sawflies, Cathayxyela extensa gen. et sp. nov. and Aequixyela immensa gen. et sp. nov., from the Middle Jurassic Jiulongshan Formation of southeastern Inner Mongolia, China, are assigned to the subfamily Xyelinae （Hymenoptera, Xyelidae）. Cathayxyela gen. nov. can be distinguished by the third antennal article longer than the head; mesoprescutum and mesoscutellum nearly equal in length; the forewing with Sc meeting C before the junction of 1-M and 1- Rs; a weak and narrow pterostigma; and 3-Cu at least 1.5 times longer than the lm-cu. Aequixyela gen. nov. is characterized by the third antennal article nearly as long as the head; the forewing with Rs＋M approximately equal to 2-Rs in length; 2m-cu inclined toward the wing base and nearly reaching the middle of cell 3rm; lm-cu as long as the 2-Cu and 3-Cu; and the cell 2cua of regular hexagonal shape. 相似文献
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Qi Zhang Alexandr P. Rasnitsyn Bo Wang Haichun Zhang 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(6):736-747
The Burmese amber assemblage of Hymenoptera with its 47 constituent families is now the richest in Cretaceous. A collection of Burmite (Burmese amber) from the Hukawng Valley, Myanmar at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences was examined, revealing that Burmite inclusions contain a very highly diverse hymenopteran fauna with as many as ten families found new for the Burmese fossil assemblage. The mid-Cretaceous hymenopteran fauna of Burmese amber is revised at the family level. A high level of the first family occurrences and endemism is demonstrated suggestive of an insular syndrome affected the mid-Cretaceous Burmese biome, as well as somewhat contradictory features in composition of the hymenopteran families there. 相似文献